ERBB2 and neoplasm: Among those with IHC 2+/HER2 amplified tumours (Groups 1, 2 and 3), ER-negativity was identified as an independent predictor of pCR (ER negative versus positive; OR, 11.80; 95%CI, 1.38–101.00; p = 0.02) which remained the case in Group 1 alone (ER negative versus positive; OR, 3.71; 95% CI, 1.28–10.70; p = 0.02).